Bricks are used as a refractory material for high temperature furnaces without posing any serious problem in terms of the ability to resist fire. Thus, they have been producing a long service life extending over many years. In recent years, efforts have been devoted to perfection of a technique for forming such bricks in lighter weight and smaller thickness with a view to diminishing such devices as furnaces and such structural members as tunnels in terms of mass, enhancing working efficiency copiously, and further enabling repair, when necessary, to be attained with simplicity.
The official gazette of JP-A-62-288,183 discloses a method for producing a fire-resistant composite material possessing satisfactory surface strength and comprising a thin fire-resistant layer by frame-spraying a refractory ceramic substance on a shaped article of fire-resistant fibers. Specifically, what is obtained by flame spraying in a plasma jet a zirconia powder having a particle diameter of not more than 0.3 mm on the surface of a zirconia fiber blanket (the shaped article of fire-resistant fibers) as illustrated in FIG. 2 inserted in the official gazette thereby forming thereon a rigid dense layer of zirconia measuring 2 mm in thickness and manifesting exclusively therein an apparent porosity of 5% and a bending strength of 150 kg/cm2 is disclosed. In this disclosure is given a description to the effect that only the surface layer 2 mm in thickness in the whole zirconia fiber refractory composite possesses a rigid texture and the remainder thereof retains a fluffy state which is peculiar to fibers.
Indeed, the use of the fire-resistant composite material for clean firing light-weight furnace members, ceiling members for the production of electronic elements and ceramic elements, and ceiling members in high-temperature furnaces which have comparatively mild use conditions is described. This fire-resistant composite material, however, is deficient in endurableness when it is used at such sites as impose severe use conditions. When the fiber blanket is used as a shaped article of fire-resistant fibers, this fiber blanket and a fire-resistant ceramic substance to be used jointly therewith are liable to peel because their bonding strength is weak. In the existing state of technique, a fire-resistant heat insulating material which excels in endurableness (specifically, ability to resist heat, ability to resist slag, ability to resist molten iron, ability to resist wear, and ability to resist mechanical impacts) remains yet to be discovered.
It is, therefore, an object of this invention to provide a fire-resistant heat insulating material which excels in heat-resisting property, slag-resisting property, molten iron-resisting property, wear-resisting property, and mechanical impact-resisting property.
Another object of this invention is to provide a fire-resistant heat insulating material which can be extensively utilized for walls, ceilings, lids, and covers in various kilns (including those for metals other than iron and steel) such as heating furnaces and hot air ovens, various kinds of flues, and automobile tunnels which impose severe work conditions.
Still another object of this invention is to provide a fire-resistant heat insulating material which realizes a light weight and a small thickness with a view to diminishing such devices as furnaces and such structural members as tunnels in terms of mass, enhancing working efficiency copiously, and further enabling repair, when necessary, to be attained with simplicity.